Rapid cycle pressure swing adsorption oxygen concentration method and apparatus

Abstract

A rapid pressure swing adsorption oxygen concentrator is provided having a plurality of at least three sieve beds cycled in sequence such that each is pressurized during one segment of a cycle and depressurized during a plurality of segments of a cycle while the other sieve beds are being sequentially pressurized. Preferably, approximately six sieves are provided and pressurized in sequence, with each being pressurized for approximately 60° of the cycle and depressurized for from about 270° to 300° of the cycle. Each sieve is thereby pressurized for about one to two seconds and depressurized for about five to ten seconds. By utilizing the ability of the sieve material to adsorb faster than it can desorb gas, high output of up to 96% pure oxygen results with a low sieve volume and low power consumption.

Therefore, the following is claimed: 
     
       1. A rapid pressure swing adsorption concentrator comprising: a plurality of at least three molecular sieves connected to operate in sequence in a cycle during which each sieve is pressurized to a pressure higher than atmospheric pressure, each sieve having an inlet side and an outlet side;   valve means for operating each of the sieves sequentially through the cycle such that each sieve has a venting subcycle during which the sieve is vented substantially to atmospheric pressure from the inlet side thereof and remaining portion of the cycle during which the sieve is pressurized from its inlet side and exchanges product rich gas at its outlet side, with each sieve substantially being in the remaining portion of its cycle when a majority of the other sieves are simultaneously in their respective venting subcycles.   
     
     
       2. The concentrator of claim 1 wherein: the valve means is operative to cycle each of the sieves sequentially through the cycle such that each sieve has a pressurization subcycle, included in said remaining portion of the cycle, of approximately one to two seconds and a depressurization subcycle, which includes the venting subcycle, of approximately five to ten seconds.   
     
     
       3. The concentrator of claim 1 wherein: the valve means is operative to cycle each of the sieves sequentially through the cycle such that each sieve has a pressurization subcycle, included in said remaining portion of the cycle, of approximately one to two seconds and a depressurization subcycle, which includes the venting subcycle, of approximately five times as long as the pressurization subcycle.   
     
     
       4. The concentrator of claim 1 wherein: the valve means is operative to cycle each of the sieves sequentially through the cycle such that each sieve has a pressurization subcycle, included in said remaining portion of the cycle, of less than approximately two seconds and a depressurization subcycle, which includes the venting subcycle, of more than approximately five seconds.   
     
     
       5. The oxygen concentrator of claim 4 wherein the at least one valve assembly further comprises: at least one outlet side valve assembly having a product outlet port, at least one sieve outlet port connected to the outlet sides of each of the sieves, and outlet side ducts selectively interconnecting the ports of the outlet side valve such that the outlet side of each of the sieves is, between two input depressurization subcycles thereof, connected to the product outlet for an output subcycle of the sieve, and to the outlet side of other of the plurality of the sieves for a reverse flow subcycle thereof.   
     
     
       6. The concentrator of claim 1 wherein: the plurality of molecular sieves includes N molecular sieves, where N equals at least 3, connected to operate in sequence in the cycle, with each sieve having a pressurization subcycle, included in said remaining portion of the cycle, that is not more than approximately 360/N° in duration and a depressurization subcycle, which includes the venting subcycle, that is not more than and not substantially less than approximately 360×(N-1)/N° in duration.   
     
     
       7. The concentrator of claim 1 wherein: the plurality of molecular sieves includes 6 molecular sieves connected to operate in sequence in a cycle, with each sieve having a pressurization subcycle, which is included in said remaining portion of the cycle, that is not more than approximately 60° in duration and a depressurization subcycle, which includes the venting subcycle, that is not between 270° and 300° in duration.   
     
     
       8. The concentrator of claim 1 further comprising: valving and interconnecting ductwork between the sieves and a common output having a volume that is approximately 2%, and not more than approximately 5% of the output per cycle of the sieves.   
     
     
       9. The concentrator of claim 1 wherein: the venting subcycle is at least approximately four and one-half seconds.   
     
     
       10. The concentrator of claim 1 wherein: the plurality of molecular sieves includes N molecular sieves, where N is greater than or equal to 3, connected to operate in sequence in the cycle, with each sieve having a pressurization subcycle, which is included in said remaining portion of the cycle, that is not more than approximately 360/N° in duration, the venting subcycle being not more than approximately 360×(N-1)/N° in duration and not substantially less than approximately (N+1)/2N° in duration.   
     
     
       11. An oxygen concentrator comprising: a plurality of more than two molecular sieves each sieve having an inlet side and an outlet side;   a pump having an ambient air intake connected to atmosphere and a high pressure outlet;   at least one valve assembly having an inlet port connected to the high pressure outlet of the pump, a low pressure outlet port, at least one sieve port connected to the inlet sides of each of the sieves, and inlet side ducts selectively interconnecting the ports such that the inlet side of each of the sieves is connected to the high pressure outlet of the pump during an inlet pressurization subcycle thereof and to the low pressure outlet during an inlet depressurization subcycle thereof; and   a valve control connected to the valve assembly and configured to operate the valve assembly in a cycle that includes alternating the inlet pressurization and depressurization subcycles for each sieve, with each inlet pressurization subcycle being not more than half the duration of the inlet depressurization subcycle of the sieve, with the inlet pressurization subcycles of at least two other sieves of the plurality totally occurring during the inlet depressurization cycle of each sieve.   
     
     
       12. The oxygen concentrator of claim 11 wherein: the inlet pressurization subcycle is not more than one third the duration of the inlet depressurization subcycle of each sieve.   
     
     
       13. The oxygen concentrator of claim 11 wherein: the inlet pressurization subcycle is not more than one fourth the duration of the inlet depressurization subcycle of each sieve.   
     
     
       14. The oxygen concentrator of claim 11 wherein: the pressurization inlet subcycle is not more than one fifth the duration of the inlet depressurization subcycle of each sieve.   
     
     
       15. The oxygen concentrator of claim 11 wherein: the inlet pressurization subcycles of all other sieves of the plurality substantially totally occur during the inlet depressurization cycle of each sieve. 
     
     
       16. The oxygen concentrator of claim 11 wherein: the inlet pressurization subcycle of each sieve is between one sixth and one tenth the duration of the cycle.   
     
     
       17. The oxygen concentrator of claim 11, wherein: the plurality of sieves includes N sieves, where N is an interger greater than 2; and   the inlet pressurization subcycle is not more than 1/Nth the duration of the inlet depressurization subcycle of each sieve.   
     
     
       18. The oxygen concentrator of claim 11 wherein the at least one valve assembly further comprises: at least one outlet side valve assembly having a product outlet port, at least one sieve outlet port connected to the outlet sides of each of the sieves, and outlet side ducts selectively interconnecting the ports of the outlet side valve such that the outlet side of each of the sieves is, between two input depressurization subcycles thereof, connected to the product outlet for an output subcycle of the sieve, and to the outlet side of an other of the plurality of the sieves for a subcycle thereof.   
     
     
       19. A rapid pressure swing adsorption oxygen concentrator for producing oxygen of at least ninety percent purity at a rate of in the approximate range of two to five liters per minute, the apparatus comprising: an air compressor having a compressor outlet;   a product outlet;   a plurality of molecular sieves having a total volume of less than approximately one liter, each sieve having an inlet side and an outlet side;   outlet-side valves connected to the outlet sides of each of the sieves and the product outlet;   inlet-side valves connected to the inlet sides of each of the sieves, the air compressor outlet and atmosphere;   a valve cycle control connected to the inlet-side valves and to the outlet-side valves to operate each of the sieves in a cycle of not longer than approximately twelve seconds with the sieves phased relative to each other at approximately equal intervals around the cycle; and   the valve cycle control being programmed to operate each one of the sieves through a sequence of subcycles, including:   (a) a venting subcycle of at least four and one-half seconds duration during which the sieve is vented from its inlet side through one of the inlet-side valves and substantially to atmosphere,   (b) an inlet subcycle during which the sieve is pressurized with air from the compressor outlet through one of the inlet-side valves into the inlet side of said one of the sieves   (c) an outlet subcycle during which oxygen rich gas is output from the outlet side of said one of the sieves through one of the outlet-side valves to the product outlet,   (d) a pair of equalization subcycles during which (1) oxygen rich gas is output from the outlet side thereof through one of the outlet-side valves and into the outlet side of one of the other sieves without venting the other sieve from its inlet side to atmosphere, and (2) oxygen rich gas is input to the outlet side of said one of the sieves through one of the outlet-side valves from the outlet side of another one of the sieves without venting said one of the sieves from its inlet side to atmosphere, and   (e) a pair of purge subcycles during which (1) oxygen rich gas output from the outlet side thereof through one of the outlet-side valves and into the outlet side of one of the other sieves while gas is venting from its inlet side of such other sieve to atmosphere, and (2) oxygen rich gas is input to the outlet side thereof through one of the outlet valves from the outlet side of another one of the sieves while gas   is venting from the inlet side of said one of the sieves through one of the inlet-side valves to atmosphere and;   the inlet subcycle (b), the outlet subcycle (c), the equalization subcycles (d)(1) and (d)(2) and the purge subcycle (e)(1) for each one of the sieves collectively occupying a portion of the cycle that is shorter in duration than the venting subcycle (a).